DESCRIPTION: Based on preliminary results the P.I. has proposed an interesting and reasonable central hypothesis, that CAPS acts on membranes to facilitate membrane interactions or fusion by interacting with PIP2. The P.I. proposes to test this hypothesis by addressing four specific aims. The goal of specific aim 1 is to characterize the mechanism of CAPS action. The goal of specific aim 2 is to begin to analyze the structure of CAPS and to investigate conformational changes in CAPS upon binding to PIP2. The goal of specific aim 3 is to characterize the CAPS null phenotype in neural cells. The goal of specific aim 4 is to characterize a new cytosolic factor that may be involved in triggering fusion.